Fix RedundantNullabilityCheck for nested types

paper-checkstyle/src/main/java/io/papermc/checkstyle/checks/RedundantNullabilityCheck.java

@@ -31,10 +31,20 @@ public int[] getRequiredTokens() {
 
     @Override
     public void visitToken(final DetailAST ast) {
-        final boolean pkgIsNullMarked = Util.isPackageInfoAnnotated(Path.of(this.getFilePath()), NullabilityAnnotationsCheck::isNullMarkedAnnotation);
         final DetailAST nullMarkedAnnotation = NullabilityAnnotationsCheck.getNullMarkedAnnotation(ast);
-        if (pkgIsNullMarked && nullMarkedAnnotation != null) {
+        if (nullMarkedAnnotation == null) {
+            return;
+        }
+        final boolean pkgIsNullMarked = Util.isPackageInfoAnnotated(Path.of(this.getFilePath()), NullabilityAnnotationsCheck::isNullMarkedAnnotation);
+        if (pkgIsNullMarked) {
             this.log(nullMarkedAnnotation.getLineNo(), ast.getColumnNo() - 1, "Redundant NullMarked annotation");
+            return;
+        }
+        for (DetailAST parentDef = Util.getEnclosingTypeDeclaration(ast); parentDef != null; parentDef = Util.getEnclosingTypeDeclaration(parentDef)) {
+            if (NullabilityAnnotationsCheck.getNullMarkedAnnotation(parentDef) != null) {
+                this.log(nullMarkedAnnotation.getLineNo(), ast.getColumnNo() - 1, "Redundant NullMarked annotation");
+                return;
+            }
         }
     }
 }

paper-checkstyle/src/test/java/io/papermc/checkstyle/checks/TestRedundantNullabilityCheck.java

@@ -0,0 +1,17 @@
+package io.papermc.checkstyle.checks;
+
+import io.papermc.checkstyle.CheckTest;
+import io.papermc.checkstyle.CheckTestBuilder;
+
+class TestRedundantNullabilityCheck {
+
+    @CheckTest("testdata.RedundantNullability")
+    void test(final CheckTestBuilder builder) {
+        builder
+            .addViolation("10:8: Redundant NullMarked annotation")
+            .addViolation("14:8: Redundant NullMarked annotation")
+            .addViolation("18:8: Redundant NullMarked annotation")
+            .addViolation("22:8: Redundant NullMarked annotation")
+            .addCheck(new RedundantNullabilityCheck());
+    }
+}

paper-checkstyle/src/testData/java/testdata/RedundantNullability.java

@@ -0,0 +1,36 @@
+package testdata;
+
+import org.jspecify.annotations.NullMarked;
+
+public class RedundantNullability {
+
+    @NullMarked
+    public static class OuterClass {
+
+        @NullMarked
+        public static class RedundantInnerClass {
+        }
+
+        @NullMarked
+        public interface RedundantInnerInterface {
+        }
+
+        @NullMarked
+        public record RedundantInnerRecord() {
+        }
+
+        @NullMarked
+        public enum RedundantInnerEnum {
+        }
+
+        public static class ValidInnerClass {
+        }
+    }
+
+    public static class NonAnnotatedOuter {
+
+        @NullMarked
+        public static class ValidAnnotatedInner {
+        }
+    }
+}